(1) Field of the Invention
This invention relates to a stripping composition and method for removing friable materials used for thermal insulation, fireproofing, acoustical insulation and decorative finishes and is particularly applicable to the removal of asbestos-containing materials.
(2) Description of the Prior Art
In recent years there has been an increasing awareness of the importance of environmental factors in carcinogenesis. The recognition of widespread environmental contamination by asbestos-containing materials has been of particular concern. Such concern is evidenced in approximately twenty Federal regulations under various laws which regulate human and environmental exposure to asbestos. Despite these regulations, large segments of the population continue to be exposed to this dangerous material especially material in friable form.
The extensive use of asbestos in commerce and industry has created a health hazard of serious consequences for persons inhaling or ingesting the substance. Since the beginning of the century, asbestos has been used as a major constituent or an important additive to many consumer products so that there are many sources of exposure to the general public. For almost forty years asbestos has been widely used in building construction having been sprayed or applied onto structural steel to retard structural collapse during fire and to ceilings and walls for purposes of acoustic and thermal insulation, decoration and condensation control. Many insulation materials consist of a mixture of asbestos and mineral-, rock-, slag-wool or fibrous glass. In other formulations wood pulp and paper fibers and non-fibrous binders such as plaster of paris, vermiculate, perlite and clay are used. Asbestos has also been used in decorative and textured-spray finishes or paints. Some of this asbestos containing material is now known to be damaged or deteriorating and releasing fibers into the building environment.
Unlike most chemical carcinogens asbestos mineral fibers persist in the environment almost indefinitely and represent a continuous source of exposure. Asbestos fibers cannot be easily destroyed or degraded. The size and shape of these fibers give them aerodynamic capability to permit them to remain suspended in air for many hours. The fibers can become suspended in the air and are then available for respiration and retention in the lung. Fibers which have settled to the floor can be reentrained by activity in the area. Thus, even though the release of fibers may be intermittent, there is a potential for continuous exposure.
Friable material is material that can be crumbled, pulverized or reduced to powder under hand pressure. Friable material may be an asbestos-containing material or it may be a material that contains other fibers such as cellulose and glass fibers. It may also include synthetic organic polymer materials in this condition. Friable asbestos material draws particular attention since it is likely to release fibers with minimum disturbance of the surface, cause serious contamination and exposure problems and it has been used in many buildings having high population densities including schools, office buildings and high-rise apartment buildings. Furthermore, as friable asbestos material ages, it can lose its cohesive strength and more readily release fibers. The asbestos content of these materials is usually found in the range of 5 weight percent to 50 weight percent. These materials were usually applied by spraying but have also been applied by troweling and brushing. They are friable in varying degrees depending on the components of the material, the amount of cement or binder added, and the method of application. Sprayed material is usually soft. Cementitious material various from soft to relatively hard. Several methods have been proposed to eliminate or substantially reduce exposure of friable asbestos material such as encapsulation, enclosure and removal. For encapsulation, the asbestos material is coated with a sealant. The sealing of sprayed asbestos surfaces involves applying material that will penetrate and envelop the fiber matrix and coat the surface portions to eliminate fallout and protect against abrasion damage as well as physical damage due to impact.
Encapsulation methods should not be employed when friable asbestos materials evidence of severe physical damage such as loose hanging material. In the enclosure approach the friable material is separated from the building environment by physical barriers such as suspended ceilings or partitions. Removal procedures require that all the friable material is taken off the underlying surface, carefully collected and disposed of by burial.
Encapsulation, enclosure and removal can be used separately or in combination. Encapsulation and enclosure are containment methods and thus the friable material remains within the building environment. Both methods should be considered as temporary measures. Removal completely eliminates the source of exposure and is, therefore, a permanent solution.
Dry removal of untreated friable asbestos material is not recommended since it results in heavy airborne asbestos contamination (fiber counts that exceed 100 fibers per cubic centimeter). Dry vacuum methods have been attempted to overcome this contamination by incorporating an exhaust filtering system to prevent pollution of the outside environment and the use of sealed containers. One drawback with the dry vacuum system is that the adhesive bond between the friable material underlying surface may be stronger than the vacuum capabilities of the equipment. Thus, the necessary initial dislodgement by scraping causes particle contamination.
Preferred removal method involes wet removal with water to lower the friability of the sprayed material and the aerodynamic capabilities of the released fibers. Asbestos exposure levels may be reduced by as much as 75 percent over dry methods. However, water is not satisfactory because of slow penetration, incomplete wetting and runoff. The runoff is not only a safety and clean-up problem, but the resulting slurry carries fibers to other areas where they can become reentrained after drying.
Generally aqueous solutions containing surfactants are used for wet removal or stripping since the water penetration into a hydrophobic fiber matrix is significantly increased. Additionally aqueous surfactant solutions greatly reduce the amount of water needed for saturation, increase the cohesiveness of the fiber matrix and individual fiber wetting. Notwithstanding these advantages the above surfactant solutions suffer the same drawback as water alone, i.e. after evaporation the fibers can become reentrained.
Therefore, a need persists for a stripping composition for friable material which overcomes the reentrainment problems, is easier to apply, improves working conditions and significantly reduces overall handling and environmental contamination.